Aspergillosis is an important cause of mortality in allogeneic HSCT. A "fungus ball" formation of Aspergillus in the bladder has seldom been reported. We report a child that underwent HSCT and developed possible disseminated aspergillosis with an intravesical "fungus ball," diagnosed by genitourinary MRI and PCR of the mass that was removed from the bladder. It is important to consider this complication in a patient with HC after HSCT. The treatment included a combination of systemic antifungal therapy along with intravesical voriconazole and surgical removal.